US5619248A - Video signal distribution system microwave radio link for transmitting double sideband phase modulated carrier signal - Google Patents
Video signal distribution system microwave radio link for transmitting double sideband phase modulated carrier signal Download PDFInfo
- Publication number
- US5619248A US5619248A US08/261,401 US26140194A US5619248A US 5619248 A US5619248 A US 5619248A US 26140194 A US26140194 A US 26140194A US 5619248 A US5619248 A US 5619248A
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- US
- United States
- Prior art keywords
- signal
- phase
- amplitude
- microwave
- distribution system
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N7/00—Television systems
- H04N7/20—Adaptations for transmission via a GHz frequency band, e.g. via satellite
Definitions
- the present invention relates to video signal distribution systems, and in particular to such systems including point-to-point radio links.
- a microwave point-to-point radio link over which said composite signal is arranged to be transmitted as double side-band phase modulation of a single microwave carrier signal.
- FIG. 1 shows a transmitter arrangement schematically
- FIG. 2 shows a receiver arrangement
- the first part of the transmitter arrangement consists of a source 1 of millimeter wave power sufficient to drive the modulator/upconverter.
- a source 1 of millimeter wave power sufficient to drive the modulator/upconverter.
- This may be a stabilised GUNN oscillator, synthesised source or any convenient method known to the art with stability and spectral purity adequate for the application.
- the output of the source 1 is taken via a low pass filter 2 to limit the level of even order harmonics of the source frequency.
- the signal is split into two paths by means of a -3 dB, 180° hybrid coupler 3.
- the carrier reference path is fed via a phase trimmer 4 to the input port of a second reversed -3 dB, 180° coupler 5.
- the modulation path takes the output from the second port of the first coupler 3 and feeds this signal via a phase shifter 6 and a level set attenuator 7 to a balanced modulator 8.
- the modulator match is isolated from the modulation path by means of microwave isolators 9 and 10 on its input and output ports respectively.
- the modulation port of the modulator 8 is fed with the desired amplitude modulated intelligence at the same frequency and channel spacing as that of the cable video signal.
- the action of the modulator is to impose amplitude modulation of the microwave carrier at the modulation rates of the complete band of cable video signals.
- both the amplitude and phase of the superposed modulation may be adjusted by means of the level set attenuator 7 and the phase shifter 6 in the modulation path.
- the superposed modulation may be adjusted so as to exactly represent pure amplitude modulation across the working bandwidth of the modulator.
- the modulator controls may be used to optimise the overall performance of the said chain by means of the inherent capability of the said modulator to provide any combination of modulation between pure phase modulation and pure amplitude modulation.
- the modulation dement itself In order to generate pure DSB phase modulation the modulation dement itself must be so balanced as to produce amplitude modulated double sidebands with the carrier component suppressed by a minimum of -50 dB of the source input power to the modulator input port. This is to ensure that the carrier leakage power at the reinsertion point 5 is below the level at which the vectoral recombination of the leakage component of the carrier with the desired reinsertion component would produce envelope modulation of the combined signal due to the phase differences between the two paths. Also, the delay through the two paths must be equalised by means of additional broadband delay in the carrier phasing path. The purpose of the above two actions is to ensure that the optimum phase relationship can be achieved between the lower sideband, the carrier and the upper sideband.
- the directivity of the couplers 3 and 5 used to construct the modulator, together with microwave isolators 9 and 10 must be sufficient to ensure that reverse isolation through both the direct and coupled paths, exceeds the required dynamic range of the complete modulator.
- an amplifier 11 can be used, post the modulator and before the coupler 5 recombining the sidebands with the carrier.
- the specification for the linearity of this amplifier 11 is not critical to the operational linearity of the recombined output signal.
- the 2nd and 3rd order components will be dealt with as will be explained.
- the essentially narrowband nature of the signal at the microwave frequency ensures that the majority of cross products fall out of band, reducing the occurrence of triple beat products to an acceptable level in the modulator output.
- the modulator with a source of sufficient power as a stand-alone microwave transmitter, directly feeding its output to an antenna.
- the modulator can be adjusted so as to transform the amplitude modulation on the coupled path into DSB phase modulation at the output port, with the modulation and all its components exactly representing those expected from phase modulation as expressed below; namely:
- the output of the modulator containing these components may be passed through a radio frequency amplitude limiter or the amplifier 11 may be a limiting amplifier, to remove the amplitude modulation at the 2nd and higher even order harmonics at the modulation frequency or frequencies.
- the output of the amplifier 11 may be passed through a band-defining filter 12 such that all components, from the 3rd harmonic of the lowest desired modulation frequency upwards, are eliminated.
- the outputs of two or more modulators may be combined to give a wide-band output composed only of phase modulation with respect to the carrier term. This may then be amplified by means of any suitable microwave amplifying means of sufficient bandwidth to avoid PM to AM conversion to the desired power level for transmission.
- the minimum number of modulators required to carry the full cable RF video band width of 55-550 MHz is two. Based on the performance of the existing modulator, the maximum required, to carry two banks of 25 channels each, would be three.
- the carrier component in the transmitted signal is used to lock the demodulating oscillator to the transmitted carrier, thereby ensuring that the signal to noise degradation of the system is gradual, rather than catastrophic.
- phase modulation system with its rejection of the inherent amplitude modulation produced at the desired modulation index, maximises the number of channels that can be upconverted via a single modulator with linearity sufficient to avoid the production of intermodulation products which would degrade the final system dynamic range.
- phase modulation is seen by all amplifying elements within the system, the production of intermodulation products due to amplitude non-linearities within these elements is minimised.
- Any residual amplitude modulation of the output signals of the modulator may be detected by a broad band detector 13 and fed back to the phase trimmer varactor 4 to adjust the phase of the reinserted carrier component.
- a single product detector may be used in the receiver to demodulate all the channels with high linearity due to the small percentage bandwidth of the signal at the intermediate frequency and the high degree of quadrature maintained by the locking of the demodulation oscillator to the carrier term in the I.F. signal.
- the receiver configuration is shown in FIG. 2.
- An I.F. limiter or limiting amplifier is used to separate the AM and PM functions of the receiver.
- the threshold performance is identical to that of a common FM system; for relatively small changes in S/N, large picture disturbances of the type known as ⁇ sparklies ⁇ occur.
- the advantage of the DSB phase modulated system is that the picture threshold quality degrades in exactly the same manner as that of an DSB AM system, providing that the carrier locking system threshold is maintained below that of the frame and colour synchronisation threshold of the demodulators in the television receiver for the sideband intelligence.
- the carrier synchronisation bandwidth is significantly less than that of the video demodulation bandwidth, carrier levels lower than the sidebands can be supported, providing that due account is taken of the maximum phase modulation index used; which must be such that amplitude disturbance of the carrier term, found from classical phase modulation theory, is below the AM to PM conversion threshold of the synchronised oscillator in the receiver.
- a receiver designed so as to meet the above criteria is then the optimum for the demodulation of the proposed phase modulation system, it being understood that all other parts of the receiver represent the best available techniques from the state of the art for the required overall performance.
Abstract
Description
Claims (5)
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB939313969A GB9313969D0 (en) | 1993-07-06 | 1993-07-06 | Video signal distribution system |
GB9313969 | 1993-07-06 | ||
GB9406185 | 1994-03-29 | ||
GB9406185A GB9406185D0 (en) | 1993-07-06 | 1994-03-29 | Video signal distribution system |
Publications (1)
Publication Number | Publication Date |
---|---|
US5619248A true US5619248A (en) | 1997-04-08 |
Family
ID=26303196
Family Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US08/261,401 Expired - Fee Related US5619248A (en) | 1993-07-06 | 1994-06-17 | Video signal distribution system microwave radio link for transmitting double sideband phase modulated carrier signal |
US08/261,455 Expired - Fee Related US5555016A (en) | 1993-07-06 | 1994-06-17 | Video signal distribution system |
Family Applications After (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US08/261,455 Expired - Fee Related US5555016A (en) | 1993-07-06 | 1994-06-17 | Video signal distribution system |
Country Status (6)
Country | Link |
---|---|
US (2) | US5619248A (en) |
EP (1) | EP0633695B1 (en) |
CA (1) | CA2126825A1 (en) |
CZ (1) | CZ287309B6 (en) |
DE (1) | DE69421648T2 (en) |
GB (1) | GB2282737B (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5930678A (en) * | 1996-05-13 | 1999-07-27 | Lucent Technologies Inc | Intermodulation distortion reduction method and apparatus |
Families Citing this family (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP3118419B2 (en) * | 1996-06-07 | 2000-12-18 | 株式会社ケンウッド | AM data multiplex modulator |
US5953043A (en) * | 1996-08-09 | 1999-09-14 | Shaw; Lew | Signal transmission system |
US20030119473A1 (en) * | 1998-11-09 | 2003-06-26 | Smith Stephen H. | Adjustable balanced modulator |
US6934514B2 (en) * | 2001-06-12 | 2005-08-23 | Spx Corporation | System for transmitting digital signals with FM signals |
US8831073B2 (en) | 2009-08-31 | 2014-09-09 | Sony Corporation | Wireless transmission system, wireless communication device, and wireless communication method |
Citations (11)
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US3778718A (en) * | 1972-04-28 | 1973-12-11 | Avco Corp | Modulation system |
JPS5583306A (en) * | 1978-12-20 | 1980-06-23 | Fujitsu Ltd | Phase modulator |
US4410911A (en) * | 1982-07-14 | 1983-10-18 | Telease, Inc. | Multiple signal transmission method and system, particularly for television |
WO1984002044A1 (en) * | 1982-11-10 | 1984-05-24 | Avnet Inc | Microwave communications system |
JPS62294346A (en) * | 1986-06-13 | 1987-12-21 | Sharp Corp | Mictowave data transmission equipment |
JPH01303986A (en) * | 1988-06-01 | 1989-12-07 | Matsushita Electric Ind Co Ltd | Television signal processing method |
US5065340A (en) * | 1989-05-19 | 1991-11-12 | Boria John I | Coherent gate vesta energy processor |
US5077542A (en) * | 1989-12-11 | 1991-12-31 | L'etat Francais (Cnet) | Transmission system with suppressed carrier signal amplitude modulation preserving the polarity of the transmitted signal, and corresponding transmitter and receiver |
US5148279A (en) * | 1991-03-18 | 1992-09-15 | Gabor William D | Fifty channel television transmitter |
US5214390A (en) * | 1992-03-16 | 1993-05-25 | Scientific-Atlanta, Inc. | Method and apparatus for partial response demodulation |
US5317288A (en) * | 1992-12-15 | 1994-05-31 | Space Systems/Loral, Inc. | Continuously variable electronically controlled phase shift circuit |
Family Cites Families (8)
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GB606145A (en) * | 1945-11-21 | 1948-08-06 | Eric Peter Rudkin | Improvements in or relating to television systems |
US4058769A (en) * | 1974-07-05 | 1977-11-15 | Alderman Robert J | Modulation system with carrier control |
US3971991A (en) * | 1974-09-04 | 1976-07-27 | Zenith Radio Corporation | Television tuning system with varactor malfunction detection |
US4312064A (en) * | 1979-01-29 | 1982-01-19 | The Anaconda Company | Modified vestigial side band transmission system |
JPH0681744B2 (en) * | 1986-10-06 | 1994-10-19 | 三菱化成株式会社 | Method for producing 2,4-dioxyquinoline derivative |
FR2607769B1 (en) * | 1986-12-08 | 1989-02-03 | Alsthom | SYSTEM FOR TWO-WAY TRANSMISSION OF INFORMATION BETWEEN A GROUND STATION AND A STATION ON A RAIL VEHICLE |
JPH027624A (en) * | 1988-06-24 | 1990-01-11 | Furuno Electric Co Ltd | Dsb transmitter |
US5006926A (en) * | 1988-10-03 | 1991-04-09 | North American Philips Corporation | High definition multiple analog component amplitude modulated television transmission system |
-
1994
- 1994-06-17 US US08/261,401 patent/US5619248A/en not_active Expired - Fee Related
- 1994-06-17 US US08/261,455 patent/US5555016A/en not_active Expired - Fee Related
- 1994-06-27 CA CA002126825A patent/CA2126825A1/en not_active Abandoned
- 1994-06-30 EP EP94304788A patent/EP0633695B1/en not_active Expired - Lifetime
- 1994-06-30 DE DE69421648T patent/DE69421648T2/en not_active Expired - Fee Related
- 1994-07-04 CZ CZ19941626A patent/CZ287309B6/en not_active IP Right Cessation
- 1994-07-05 GB GB9413522A patent/GB2282737B/en not_active Expired - Fee Related
Patent Citations (13)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3778718A (en) * | 1972-04-28 | 1973-12-11 | Avco Corp | Modulation system |
JPS5583306A (en) * | 1978-12-20 | 1980-06-23 | Fujitsu Ltd | Phase modulator |
US4410911A (en) * | 1982-07-14 | 1983-10-18 | Telease, Inc. | Multiple signal transmission method and system, particularly for television |
WO1984002044A1 (en) * | 1982-11-10 | 1984-05-24 | Avnet Inc | Microwave communications system |
US4475242A (en) * | 1982-11-10 | 1984-10-02 | Marc Rafal | Microwave communications system |
US4475242B1 (en) * | 1982-11-10 | 1986-08-12 | ||
JPS62294346A (en) * | 1986-06-13 | 1987-12-21 | Sharp Corp | Mictowave data transmission equipment |
JPH01303986A (en) * | 1988-06-01 | 1989-12-07 | Matsushita Electric Ind Co Ltd | Television signal processing method |
US5065340A (en) * | 1989-05-19 | 1991-11-12 | Boria John I | Coherent gate vesta energy processor |
US5077542A (en) * | 1989-12-11 | 1991-12-31 | L'etat Francais (Cnet) | Transmission system with suppressed carrier signal amplitude modulation preserving the polarity of the transmitted signal, and corresponding transmitter and receiver |
US5148279A (en) * | 1991-03-18 | 1992-09-15 | Gabor William D | Fifty channel television transmitter |
US5214390A (en) * | 1992-03-16 | 1993-05-25 | Scientific-Atlanta, Inc. | Method and apparatus for partial response demodulation |
US5317288A (en) * | 1992-12-15 | 1994-05-31 | Space Systems/Loral, Inc. | Continuously variable electronically controlled phase shift circuit |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5930678A (en) * | 1996-05-13 | 1999-07-27 | Lucent Technologies Inc | Intermodulation distortion reduction method and apparatus |
Also Published As
Publication number | Publication date |
---|---|
CZ287309B6 (en) | 2000-10-11 |
CZ162694A3 (en) | 1996-11-13 |
GB2282737A (en) | 1995-04-12 |
US5555016A (en) | 1996-09-10 |
CA2126825A1 (en) | 1995-01-07 |
DE69421648D1 (en) | 1999-12-23 |
GB9413522D0 (en) | 1994-08-24 |
EP0633695B1 (en) | 1999-11-17 |
EP0633695A1 (en) | 1995-01-11 |
DE69421648T2 (en) | 2000-03-09 |
GB2282737B (en) | 1998-02-18 |
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Legal Events
Date | Code | Title | Description |
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AS | Assignment |
Owner name: PLESSEY SEMICONDUCTORS LIMITED, UNITED KINGDOM Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:HOBDEN, MERVYN KEITH;REEL/FRAME:007176/0176 Effective date: 19940928 Owner name: PLESSEY SEMICONDUCTORS LIMITED, UNITED KINGDOM Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:SPENCER, DAVID GRAHAM;REEL/FRAME:007176/0178 Effective date: 19940928 Owner name: MCEL P.L.C., UNITED KINGDOM Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:SPENCER, DAVID GRAHAM;REEL/FRAME:007176/0178 Effective date: 19940928 Owner name: MCEL P.L.C., UNITED KINGDOM Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:RHODES, JOHN G.L., (DECEASED) BY TURNER, RONALD, EXECUTOR;REEL/FRAME:007179/0124 Effective date: 19940928 Owner name: MCEL P.L.C., UNITED KINGDOM Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:HOBDEN, MERVYN KEITH;REEL/FRAME:007176/0176 Effective date: 19940928 Owner name: PLESSEY SEMICONDUCTORS LIMITED, UNITED KINGDOM Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:RHODES, JOHN G.L., (DECEASED) BY TURNER, RONALD, EXECUTOR;REEL/FRAME:007179/0124 Effective date: 19940928 |
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Owner name: EEV LIMITED, UNITED KINGDOM Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:PLESSEY SEMICONDUCTORS LIMITED;REEL/FRAME:008811/0673 Effective date: 19971030 |
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FPAY | Fee payment |
Year of fee payment: 4 |
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REMI | Maintenance fee reminder mailed | ||
LAPS | Lapse for failure to pay maintenance fees | ||
STCH | Information on status: patent discontinuation |
Free format text: PATENT EXPIRED DUE TO NONPAYMENT OF MAINTENANCE FEES UNDER 37 CFR 1.362 |
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FP | Expired due to failure to pay maintenance fee |
Effective date: 20050408 |